Polyethylene glycol/polycation block copolymers

Abstract

The invention provides block copolymers formed of poly(ethylene glycol) segments and poly(amino acid derivative) segments having side chains of at least one kind of specific amine residue. The invention also provides polyion complexes of such copolymers with polynucleotides and the like. These block copolymers are useful as carriers for in vivo delivery of active substances such as DNA.

Description

TECHNICAL FIELD [0001] This invention relates to block copolymers having polyethylene glycol structural portion as a hydrophilic segment and polyamino acid structural portion having amine residue side chains of various structures as a cationic segment; and also to polyion complexes of the copolymers with nucleic acid or anionic proteins. BACKGROUND ART [0002] A polyethylene glycol / polycation block copolymer represented by polyethylene glycol-block-poly(L-lysine) which is a cationic block copolymer spontaneously forms a spherical micelle with an anionic macromolecule, due to the electrostatic interaction acting between the two in water as a driving power. This particle has a diameter of several tens nanometers and a core-shell structure, the core (or inner nucleus) being formed of polyion complex of cation and anion, and the shell (or outer shell) being a polyethylene glycol (which may be hereafter abbreviated as “PEG”) layer. The particle is referred to as polyion complex (PIC) mice...

AI Technical Summary

Benefits of technology

[0030] This invention enables to control those factors which affect gene transfer effectivity such as the condensed state of genes in PIC micelles, release rate of the genes from the micelles, proton-sponge effect, micelle stability and the like. The invention enables provision of PIC micelles having higher gene transfer effectivity. The invention also enables provision of more useful non-viral gene vectors.

[0031]FIG. 1 is a photograph in place of a drawing, showing the result of electrophoreses of solutions of MeO-PEG-MOPA and p-DNA blended at various N / P ratios (N / P ratio: 0, 10, 5, 4, 3, 2, 1, 0, respectively, from the left). (Here N / P=0 signifies the lane in which p-DNA only is migrated.)

[0032]FIG. 2 is a photograph in place of a drawing showing the result of electrophoreses of solutions of MeO-PEG-DET and p-DNA blended at various N / P ratios (N / P ratio: 10, 5, 3, 2, 1, 0.5, 0.25, 0, respectively, from the left). (Here N / P=0 signifies the lane in which p-DNA only is migrated.)

[0033]FIG. 3 is a graph showing particle size distribution of associated particles formed of MeO-PEG-MOPA and p-DNA, as measured by means of dynamic light scatting (DLS).

[0034]FIG. 4 is a graph showing the measured result of N / P ratio dependency of particle diameter of associated particles formed of MeO-PEG-MOPA and p-DNA.

[0035]FIG. 5 is a graph showing particle size distribution of associated particles formed of MeO-PEG-DET and p-DNA, as measured by means of dynamic light scatting (DLS).

Problems solved by technology

Although priority in developing gene vectors using such cationic block copolymers is thus clear, due to limitations on their synthesis and for other reasons, cationic block copolymers which are currently investigated do not extend beyond PEG-block-poly(L-lysine), PEG-block-poly(dimethylaminoethyl methacrylate) (see, e.g., Patent Reference 1) and PEG-block-polyethylenimine.

These PIC micelles are considerably stable under physiological conditions in general, but is actual use their stability under physiological conditions is occasionally insufficient, as exemplified by dissociation of PIC micelles under dilution after administration by intravenous injection or their interaction with serum proteins.

As aforesaid, however, heretofore the kinds of studied polycation are limited and there has been no concept of simultaneous introduction of two or more kinds of polycations to allot them different functions.

Under the circumstances, it was very difficult to control these factors.

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